1. Field of the Invention
The present invention relates to a position detecting system for detecting a position of a detecting body by applying a magnetic field to the detecting body which incorporates therein a resonance circuit (hereinafter, referred to as the “LC resonance circuit”) composed of a coil and a capacitor to detect a magnetic field (hereinafter, referred to the “resonance magnetic field”) emitted by the LC resonance circuit of the detecting body in response to the applied magnetic field.
2. Description of the Related Art
Conventionally, there has been proposed a position detecting system for detecting a position of a detecting body incorporating therein an LC resonance circuit, by detecting a magnetic field. The position detecting system of magnetic field detection type is usually provided with a magnetic field generating coil for generating a magnetic field in three-dimensional space, and a plurality of magnetic field detecting coils for detecting the magnetic field in the three-dimensional space, wherein the system applies the magnetic field of the magnetic field generating coil to the LC resonance circuit in the detecting body introduced into the three-dimensional space to thereby detect a resonance magnetic field emitted from the LC resonance circuit in the detecting body, by a plurality of magnetic field detecting coils, and thus detects a position of the detecting body in the three-dimensional space based on a magnetic field strength of the detected resonance magnetic field.
Here, when detecting the magnetic field in the three-dimensional space where the detecting body exists, the plurality of magnetic field detecting coils will detect not only the resonance magnetic field of the detecting body, but also an environmental magnetic field, such as a magnetic field of the magnetic field generating coil and the like. For this reason, the position detecting system removes, using subtraction processing or the like, a magnetic field strength of the environmental magnetic field from the magnetic field strength of the magnetic field in the three-dimensional space detected by the magnetic field detecting coil to thereby acquire the magnetic field strength of the resonance magnetic field of the detecting body. It is to be noted that the aforementioned position detecting system generates the magnetic field of the magnetic field generating coil in the three-dimensional space in a state where the detecting body does not exist, and detects by the plurality of magnetic field detecting coils the magnetic field generated in the three-dimensional space, namely, the environmental magnetic field, such as the magnetic field of the magnetic field generating coil and the like to thereby acquire the magnetic field strength of the environmental magnetic field in the three-dimensional space.
Such a position detecting system includes a system that applies a magnetic field to a detecting body, which is a capsule medical device that is thrown into a body of a subject being tested to thereby conduct a medical practice, detects an induction field (namely, resonance magnetic field), which is inducted by the applied magnetic field and emitted by the detecting body, and detects a position of the detecting body (capsule medical device) based on the detected induction field (for example, refer to Japanese Patent Application Laid-Open No. 2007-54246).